The present invention relates generally to the machining of rotating workpieces and, in particular, to a cutting insert that may be used to perform grooving, turning, boring, face grooving, face turning and cut-off operations.
Metal cutting inserts, particularly the so-called dogbone shaped varieties, which have capabilities of removing metal in both the radial and axial directions have been known to the art for several decades. This style of insert initially was ground all over and offered no topographical features to reduce cutting pressures or assist in chip control.
Chip control is important on large workpieces where significant lengths of stock are to be removed from the outside diameter of the workpiece in the axial mode. Absence of chip control during this type of operation can be inconvenient and costly.
Enhancements to the early inserts of this type offered a variety of chip controlling devices which gave a significant degree of chip control in both the radial and axial directions. These early chip control enhancements also generally narrowed the radial mode chip to ease chip ejection. However, these enhancing mechanisms caused increased levels of cutting pressure due to the location, size and style of the chip control devices.
Later advancements in the art placed a greater amount of emphasis on a combination of chip control and reduction of cutting pressure or at least one feature in the axial mode, but did not offer similar improvements in the radial mode. Still other inserts offered improvements in the radial mode, but either did not have the uniform cutting edge required to generate a flat bottom groove or did not have the capability of performing turning operations in a productive fashion. Even further, some of the chip control devices were located in such a manner or restricted in size such that they could not offer chip control over a complete range of depths of cut in the axial mode.
The present invention provides a new and improved cutting insert that is capable of performing multiple machining operations, such as turning, grooving, parting, etc. and which includes chip controlling and chip breaking surfaces which improve chip management during its use.
According to the invention, the metal cutting insert has a forward face and at least one side face. An upper boundary of the forward face joins a forward cutting surface, such that the juncture of the forward cutting surface and the forward face defines a forward cutting edge. The side face has an upper boundary which joins a side cutting surface, such that the juncture of the side cutting surface and the upper boundary of the side face defines a side cutting edge. The side cutting edge forms part of a shelf that includes chip controlling structure including a chip deflecting surface that is positioned adjacent the cutting surface. In the preferred and illustrated embodiment, the width of the chip deflecting surface increases in a direction away from the front cutting edge and the chip controlling structure further includes a plurality of recesses spaced along the chip deflecting surface.
In the preferred and illustrated embodiment, the recesses increase in size in a direction away from the forward cutting edge, such that the recess nearest the forward cutting edge is the smallest of all the recesses that form part of the chip controlling structure.
With the present invention, the metal cutting insert can be used to perform a multitude of tasks. When the tool is moved radially with respect to a rotating workpiece, the forward cutting edge generally performs a cut-off or grooving operation. When the tool is moved axially with respect to the rotating workpiece, the tool is generally performing a turning operation.
The shelf which includes the side cutting edge and associated chip controlling structure, provides enhanced chip control. The deflecting surface which is preferably positioned immediately adjacent the cutting surface induces the chip to curl. The recesses which in the preferred embodiment are positioned along the chip deflecting surface tend to provide localized stiffening of the chip which in turn causes the chip to break relatively quickly thereby reducing the chance of producing large, unmanageable chips which could interfere with the machining operation.
According to a further feature of the invention, a forward chip controlling structure is associated with the forward cutting edge. In the illustrated embodiment, the forward chip controlling structure includes a pair of spaced apart inclined surfaces which run from the corners of the insert to a position intermediate the centerline, such that a channel is formed which extends from the forward cutting edge towards an intermediate section of the cutting insert. With the disclosed construction, as the forward edge of the insert enters the rotating workpiece, a chip is generated which moves across the forward cutting edge and onto spaced apart, arcuate ridges which at least partially define the inclined surfaces. As the chip is being formed, it is supported by the spaced apart ridges, thus causing the chip to stiffen due to bending imposed in the area of a chip that is traveling over the channel where it is unsupported. As a result of the stiffening, the chip tends to break off quickly, thus, reducing the chances of producing long chips which could interfere with the machining operation.
In the exemplary embodiment, the cutting portion of the metal cutting insert includes a second side cutting edge which forms part of a second shelf. In the preferred embodiment, a second shelf includes substantially the same chip controlling structure as that of the first shelf. With the preferred construction, the insert can be used to cut in either axial direction. For example, the metal insert can be moved radially into a rotating workpiece to create a groove having a width substantially equal to the width of the metal insert. The insert can then be moved axially in either direction to widen the groove.
According to the invention, the forward cutting edge is preferably continuous and located in a common plane. With this construction, when the metal insert is moved radially into the workpiece, the bottom of the groove that it creates is substantially flat.
According to a further feature of the invention, the metal cutting insert preferably includes metal cutting portions disposed on either side of a shank portion. In the preferred construction, when one of the cutting portions is worn, the tool is removed from its tool holder and rotated 180xc2x0 in order to position the opposite, unused cutting portion into a machining position.
In the preferred construction, the insert is formed from a relatively hard material, such as carbide, cermet or ceramic. The insert may be molded using a powder metal technology that is known in the art. In the preferred embodiment, the insert is molded using known technology and is intended for single use. With the preferred construction, the cutting insert is disposed of after its cutting portions are worn and is not intended to be resharpened or remanufactured.